Increased understanding of the role of carbohydrates as recognition elements on the surface of cells has led to increased interest in the production of carbohydrate molecules of defined structure. For instance, compounds comprising the sialyl Lewis ligands, sialyl Lewis.sup.x and sialyl Lewis.sup.a are present in leukocyte and non-leukocyte cell lines that bind to receptors such as the ELAM-1 and GMP 140 receptors. Polley et al., Proc. Natl. Acad. Sci., USA, 88:6224 (1991) and Phillips et al., Science, 250:1130 (1990), see, also, U.S. Ser. No. 08/063,181.
Because of interest in making desired carbohydrate structures, glycosyltransferases and their role in enzyme-catalyzed synthesis of carbohydrates are presently being extensively studied. These enzymes exhibit high specificity and are useful in forming carbohydrate structures of defined sequence. Consequently, glycosyltransferases are increasingly employed as enzymatic catalysts in the synthesis of a number of carbohydrates used for therapeutic and other purposes (Ito et al., Pure Appl. Chem., 65:753 (1993); U.S. Pat. Nos. 5,352,670, and 5,374,541).
Synthesis of desired carbohydrate compounds has been achieved on preparative scales using enzymatic cycles using glycosyltransferases such as .beta.1,4 galactosyltransferase and .alpha.2,3 sialyltransferase (See, e.g., U.S. Pat. No. 5,374,541; WO 9425615; and Ichikawa, et al., J. Am. Chem. Soc., 114:9283-9298 (1992)).
Although fucosyltransferases have been cloned and expressed, enzymes for the production of guanosine 5-diphospho-.beta. L-fucose (GDP-fucose), the donor substrate for the fucosyltransferases are not readily available. Use of fucosyltransferase cycles would be greatly facilitated if GDP-fucose can be readily regenerated enzymatically. The present invention fulfills these and other needs.